Self-Lubricating Ball Screw

ABSTRACT

A self-lubricating ball screw comprises a nut, a screw shaft, at least one lubricating unit and at least one external oil tank. The lubricating unit is disposed in the nut, an end of the lubricating unit protrudes out of the nut and contacts the screw shaft, and another end of the lubricating unit is connected to the oil tank for absorbing the lubricating oil to the lubricating unit from the oil tank. A quick-release concave is formed in a side of the respective oil tanks, allowing for radial movement of the screw shaft. With the quick-release concave, the oil tank can be replaced at any time. The lubricating unit straddles the wipers and transmits lubricating oil to the protrusion without affecting the original arrangement of the wiper at either end of the nut, thus effectively saving the space of the oil tank, simplifying the structure and improving the maintenance efficiency.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ball screw, and more particular to aself-lubricating ball screw, wherein the oil tank is replaceable at anytime, and the lubricating unit doesn't affect the original arrangementof the wiper at either end of the nut, thus effectively saving the spaceof the oil tank, simplifying the structure and improving the maintenanceefficiency.

2. Description of the Prior Art

Since linear transmission products are being applied more and morewidely in the modern industry, various linear transmission mechanismshave widely come into human life, manufacturing factory and high scienceand technology instruments, such as linear guideway, ball screw, and thelike. Particularly in a large-scale precision mechanism are usuallyinstalled various large and small ball screws or linear guidewaysystems. Although the technology for linear transmission element isdeveloping fast, consumers still need the technology to be improveduninterruptedly. Therefore, there are still some problems to be solved.And this desire for constant improvement of technology is particularstrong in many high precision mechanism-manufacturing fields thatrequire comparative stability and quiet. Hence, the existing linearmechanism still has some technological blind spots to be improved.

A conventional ball screw lubricating system is shown in FIG. 1, whereina nut 11 is screwed on the screw shaft 10, and a wiper 111 is disposedat either side of the nut 11. Two external oil tanks 12 are screwed onthe screw shaft 10 and located at either side of the nut 11. Each of theoil tanks 12 contains an oil-containing member 121 that contacts thescrew shaft 10 for the purpose of lubrication. However, theabovementioned ball screw is impractical because of the followingreasons:

First, due to the nut 11 is provided at either side thereof with thewiper 111, and the two oil tanks 12 are located outside the nut 11, onecan imagine that most of the oil that the oil-containing member 121smears on the screw shaft 10 will be wiped off by the wipers 111. As aresult, the screw shaft cannot be lubricated effectively, and thelubricating oil will be wasted.

Second, in real use, the rotation of the screw shaft 10 will consume theoil in oil tanks 12. When the oil is used up, the user has todisassemble the screw shaft 10 from the ball screw, and then the oiltanks 12 can be replaced. Furthermore, the ball screw must be rectifiedagain. It is not only time consuming but also laborsome.

Hence, with the popularization of the linear transmission application,the demand of solving the aforementioned problems is becoming more andmore urgent, and manufacturing an easily maintained ball screw less witha good lubricating effect has become the most important selling pointthat the manufactures are striving for. Therefore, how to develop alinear transmission element more satisfying the user's needs has becomea focal point in the linear transmission unit manufacturing field.

What follows is an example of the improved technology of an existingproduct disclosed in a US patent:

FIG. 2-A shows the product disclosed in U.S. Pat. No. 6,364,058 B1,wherein a nut 13 and an oil tank 14 are screwed on the screw shaft 15,and a wiper 16 is fixed at a terminal end of the oil tank 14. The wiper16 comprises a sealing case 161, a wiper ring 162 and a cover 163 (asshown in FIG. 2-B), the wiper 16 is located at the outermost edge of thenut so as to prevent the lubricating oil from being unexpectedly stoppedout of the nut. However, this ball screw system is not only complicatedin structure, difficult to assemble, because the nut 13, the two oiltanks 14 and the wipers 16 should be screwed on the screw shaft,respectively, but also the wiper 16 has many components and its cost ishigh.

The present invention has arisen to mitigate and/or obviate theafore-described disadvantages.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to a self-lubricatingball screw that doesn't affect the original arrangement of the wiper ateither end of the nut, and can provide a good lubricating effect.

To achieve the abovementioned objective, the lubricating unit isdisposed in the nut in such a manner that an end of the lubricating unitprotrudes out of the nut and contacts the screw shaft, and another endof the lubricating unit is connected to the oil tank for absorbinglubricating oil. In this way, the lubricating unit will not affect theoriginal arrangement of the wiper at either end of the nut and canprevent the wiper from wiping off the lubricating oil, thus effectivelysaving the space of the oil tank, simplifying the structure and reducingthe assembly cost.

The secondary objective of the present invention is to a simplystructured and easily assembled self-lubricating ball screw.

The present invention is provided with an external oil tank, a side ofthe oil tank is formed with a quick-release concave that allows forpassage of the screw shaft, and an end of the oil tank is inserted inthe nut. The quick-release concave allows for quick replacement of theoil tank, thus simplifying the lubricating structure while improving theassembly efficiency.

The present invention will become more obvious from the followingdescription when taken in connection with the accompanying drawings,which show, for purpose of illustrations only, the preferred embodimentsin accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a conventional lubricating structureof a ball screw;

FIG. 2-A is an exploded view of another conventional lubricatingstructure of a ball screw;

FIG. 2-B is an exploded view of another conventional lubricatingstructure of a ball screw;

FIG. 3 is an assembly cross sectional view of a first embodiment of thepresent invention;

FIG. 4 is an exploded view of showing an oil tank in accordance with thefirst embodiment of the present invention;

FIG. 5 is a perspective view of the nut and the lubricating unit inaccordance with the first embodiment of the present invention;

FIG. 6 is a cross sectional view of showing a nut, a lubricating unitand a screw shaft in accordance with a second embodiment of the presentinvention;

FIG. 7 is an exploded view of a third embodiment of the presentinvention;

FIG. 8 is an assembly cross sectional view of the third embodiment ofthe present invention;

FIG. 9 is an assembly cross sectional view of a fourth embodiment of thepresent invention; and

FIG. 10 is an assembly cross sectional view of a fifth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The foregoing, and additional objects, features and advantages of thepresent invention will become apparent from the following detaileddescription of preferred embodiments thereof, taken in conjunction withthe accompanying FIGS. 3-5.

A self-lubricating ball screw in accordance with the present inventioncomprises a screw shaft 20, a nut 30, two lubricating units 40 and twoexternal oil tanks 50. The screw shaft is screwed in a threaded hole 31of the nut 30.

The nut 30 is defined with a receiving space 32, in an end of thereceiving space 32 is a hole 321 for reception of the screw shaft 20,and in another end of the receiving space 32 is an absorbing hole 322(in the axial direction of the nut 20) formed in the sidewall of the nut30. A positioning groove 33 is formed in the nut 30 and located adjacentthe absorbing hole 322, and in the end of the nut 30 is further defineda recess 34 for wiper. The hole 321 of the receiving space 32 is locatedmore inside the nut 30 as compared with the recess 34.

The lubricating units 40 are engaged in the receiving space 32 of thenut 30, an end of the respective lubricating units 40 is formed with aprotrusion 41 that protrudes out of the hole 321 of the receiving space32 for mating with the screw shaft 20. The lubricating units 40 eachhave an absorbing portion 42 received in the absorbing hole 322 of thereceiving space 32.

The oil tanks 50 are filled with lubricating oil and fixed at both endsof the nut 30. Each of the oil tanks 50 is formed with a protruding head51 positioned in the positioning groove 33 adjacent to the absorbinghole 322 of the nut 30 for outputting lubricating oil. The protrudinghead 51 abuts against the absorbing portion 42 of the lubricating units40. A quick-release concave 52 in a side of the respective oil tanks 50is formed correspondingly to the shape of the screw shaft 20 (the oiltank 50 is formed in the shape of a horseshoe), and the quick-releaseconcave 52 allows for radial movement of the screw shaft 20.

Two wipers 60 are engaged in the recess 34 at the end of the nut 30.

The receiving space 32 can be an elongated groove with one end open, ora concealed groove partially embedded in the nut 30, or in any otherforms as long as it can receive the lubricating units 40.

For a better understanding of the first embodiment, its operation andfunction, reference should be made then to FIGS. 3 and 4.

Since the quick-release concave 52 is formed in the side of therespective oil tanks 50, and the quick-release concave 52 allows forradial movement of the screw shaft 20, such arrangements allow for easyreplacement of the oil tanks 50. The user only needs to pull theprotruding head 51 of the oil tanks 50 out of the positioning groove 33of the nut 30, then pull the oil tanks 50 upward, the quick-releaseconcave 52 will disengage the screw shaft 20, and the oil tanks 50 canbe disassembled and replaced easily. On the other hand, the oil tanks 50also can be assembled easily in reverse order to the steps describedabove.

In addition, the wipers 60 are positioned in the recess 34 at the end ofthe nut 30, the hole 321 of the receiving space 32 is located moreinside the nut 30 as compared with the recess 34, plus the protrusion 41protrudes out of the hole 321 of the receiving space 32 and contacts thescrew shaft 20, the oil tanks 50 can use the protruding head 51 tooutput lubricating oil to the lubricating units 40, and the lubricatingunits 40 straddle the wipers 60 and transmit lubricating oil to theprotrusion 41. The external oil tanks 50 have quick-release function,the nut 30 and the wiper 60 also can be simply structured, and thewipers 60 will not wipe the lubricating oil off the screw shaft.

FIG. 6 shows a second embodiment of the present invention, and itsstructure is explained as follows:

The lubricating unit 40 is formed with two protrusions 41 for matingwith a double thread screw shaft 20, so that the lubricating oil can betransmitted more effectively. The two protrusions 41 simultaneouslycontact two or more neighboring grooves.

FIGS. 7 and 8 show a third embodiment of the present invention, and itsstructure is explained as follows:

The receiving space 32 of the nut 30 is formed by an annular groove A1,a radial through hole A2, and an axial hole A3. The annular groove A1 isconnected to the radial through hole A2, and the radial through hole A2is in communication with the axial hole A3. The annular groove A1 servesas an open hole and the axial hole A3 serves as the absorbing hole.

An annular lubricating unit A4 and a wiper 60 are positioned in theannular groove A1, respectively. A transmission unit A5 is disposed inthe radial through hole A2, and an end of the transmission unit A5contacts the annular lubricating unit A4. The oil tanks 50 each isformed with a protruding head 51 positioned in the absorbing hole(namely the axial hole A3) of the nut 30 for outputting lubricating oil.The transmission unit A5 transmits the lubricating oil from thelubricating unit 40 to the annular lubricating unit A4, and then theannular lubricating unit A4 supplies lubricating oil to the screw shaft20.

Due to the open hole (namely the annular groove A1) of the receivingspace 32 is located more inside the nut 30 as compared with the wiper60, this embodiment also can use the quick-release oil tanks 50 withoutthe problem of lubricating oil being wiped off by the wiper 60.

Referring to FIG. 9, which shows a forth embodiment of the presentinvention, wherein the protrusion 41 of the lubricating unit 40protrudes out of the hole 321 of the receiving space 32 and contacts thescrew shaft 20, and a protruded absorbing portion B1 is formed at an endof the lubricating unit 40. The absorbing portion B1 protrudes out of anend of the nut 30. When the oil tank 50 is positioned (positioningmethods include: insertion, screwing, etc) at the end of the nut 30, theabsorbing portion B1 will insert in the oil tank 50 for absorbinglubricating oil.

Referring finally to FIG. 10, which shows a fifth embodiment, the fifthembodiment is the simplest embodiment of the present invention, whichcan reduce production cost on the basis of maintaining the originalfunction, therefore it is one of the preferred embodiments of thepresent invention.

The nut 30 is defined with a receiving space 32, in an end of thereceiving space 32 is a hole 321 for mating the screw shaft 20, and inanother end of the receiving space 32 is an absorbing hole 322 (in theaxial direction of the nut 20) formed in the sidewall of the nut 30. Aradial through hole C1 is formed at a side of the receiving space 32,and is located more inside the nut 30 as compared with the recess 34.The nut 30 is further defined with a positioning groove 33 locatedadjacent the absorbing hole 322.

The lubricating unit C2 is in the shape of a rod engaged in the radialthrough hole C1 of the receiving space 32 of the nut 30, a protrusionC21 formed at an end of the lubricating unit C2 protrudes out of thehole 321 of the receiving space 32 and contacts the screw shaft 20.

The oil tanks 50 are filled with lubricating oil and fixed at both endsof the nut 30. Each of the oil tanks 50 is formed with a protruding head51 positioned in the positioning groove 33 adjacent to the absorbinghole 322 of the nut 30 for outputting lubricating oil. Since thepositioning groove 33 is connected to the radial through hole C1, theprotruding head 51 can absorb lubricating oil when it abuts against thelubricating unit C2.

The wiper 60 is fixed at the end of the nut 30.

The radial through hole C1 of this embodiment allows for easy insertionof the rod-shaped lubricating unit C2, thus effectively simplifying theassembly and reducing its cost.

The main characteristic of the present invention is that the oil tankcan be replaced easily at any time. When the oil tank is fixed at theend of the nut, lubricating oil will be transmitted from the oil tank tothe lubricating unit in the nut and then will be applied to the screwshaft, automatically.

In addition, the abovementioned receiving space can be formed by theineffective helical groove in the nut, wherein no balls pass through theineffective helical groove. Since the ineffective helical groove of thenut also mates with the effective helical groove of the screw shaft, thereceiving space can be defined in the ineffective helical groove of thenut for receiving a lubricating unit that can lubricate the effectivehelical groove of the screw shaft directly.

To summarize, the improved structure of the present invention comprisesa nut, a screw shaft, at least one lubricating unit and at least oneexternal oil tank. The lubricating unit is disposed in the nut, an endof the lubricating unit protrudes out of the nut and contacts the screwshaft, and another end of the lubricating unit is connected to the oiltank for absorbing the lubricating oil to the lubricating unit from theoil tank. A quick-release concave is formed in a side of the respectiveoil tanks, allowing for radial movement of the screw shaft. With thequick-release concave, the oil tank can be replaced at any time. Thelubricating unit straddles the wipers and transmits lubricating oil tothe protrusion without affecting the original arrangement of the wiperat either end of the nut, thus effectively saving the space of the oiltank, simplifying the structure and improving the maintenanceefficiency.

While we have shown and described various embodiments in accordance withthe present invention, it should be clear to those skilled in the artthat further embodiments may be made without departing from the scope ofthe present invention.

1. A self-lubricating ball screw comprising a screw shaft, a nut screwedon the screw shaft, at least one lubricating unit and at least one oiltank; wherein the nut is defined with a receiving space, a hole isformed in an end of the receiving space for reception of the screwshaft, and an absorbing hole is formed in another end of the receivingspace; the lubricating unit is engaged in the receiving space of thenut, an end of the lubricating unit is formed with a protrusion thatprotrudes out of the hole of the receiving space and contacts the screwshaft, the lubricating unit has an absorbing portion received in theabsorbing hole of the receiving space; and the oil tank is filled withlubricating oil and fixed at an end of the nut, lubricating oil in theoil tank contacts the absorbing portion of the lubricating unit and isabsorbed by it, a quick-release concave in a side of the oil tank isformed correspondingly to the shape of the screw shaft, allowing forradial movement of the screw shaft.
 2. The self-lubricating ball screwas claimed in claim 1, wherein a positioning groove is formed in the nutand located adjacent the absorbing hole, in an end of the nut is defineda recess for accommodation of a wiper, and the hole of the receivingspace is located more inside the nut as compared with the recess; theoil tanks is formed with a protruding head positioned in the positioninggroove adjacent to the absorbing hole of the nut for outputtinglubricating oil, the protruding head abuts against the absorbing portionof the lubricating unit; and at least one wiper is engaged in the recessof the nut.
 3. The self-lubricating ball screw as claimed in claim 1,wherein the absorbing portion protrudes out of the nut, when the oiltank is positioned, the absorbing portion will insert in the oil tankfor absorbing lubricating oil.
 4. The self-lubricating ball screw asclaimed in claim 1, wherein the receiving space of the nut is formed byan annular groove, at least one radial through hole, and at least oneaxial hole, the annular groove is connected to the radial through hole,and the radial through hole is in communication with the axial hole, theannular groove serves as an open hole and the axial hole serves as anabsorbing hole; the lubricating unit is annular; a wiper and atransmission member, the annular lubricating unit and the wiper arepositioned in the annular groove, respectively, the transmission unit isdisposed in the radial through hole, an end of the transmission unitcontacts the annular lubricating unit, the oil tank is formed with aprotruding head positioned in the absorbing hole of the nut, and anotherend of the transmission unit transmit the lubricating oil from thelubricating unit to the annular lubricating unit.
 5. Theself-lubricating ball screw as claimed in claim 2, wherein a radialthrough hole is formed at a side of the receiving space and is locatedmore inside the nut as compared with the recess, the nut is furtherdefined with a positioning groove located adjacent the absorbing hole;the lubricating unit is in the shape of a rod engaged in the radialthrough hole of the receiving space of the nut; and the oil tanks isformed with a protruding head positioned in a positioning grooveadjacent to the absorbing hole of the nut for outputting lubricatingoil, since the positioning groove is connected to the radial throughhole, the protruding head can absorb lubricating oil when it abutsagainst the lubricating unit.
 6. The self-lubricating ball screw asclaimed in claim 1, wherein the lubricating unit is formed with aplurality of protrusions for mating with a plurality of threads of thescrew shaft.
 7. The self-lubricating ball screw as claimed in claim 2,wherein the lubricating unit is formed with a plurality of protrusionsfor mating with a plurality of threads of the screw shaft.
 8. Theself-lubricating ball screw as claimed in claim 3, wherein thelubricating unit is formed with a plurality of protrusions for matingwith a plurality of threads of the screw shaft.
 9. The self-lubricatingball screw as claimed in claim 4, wherein the lubricating unit is formedwith a plurality of protrusions for mating with a plurality of threadsof the screw shaft.
 10. The self-lubricating ball screw as claimed inclaim 5, wherein the lubricating unit is formed with a plurality ofprotrusions for mating with a plurality of threads of the screw shaft.